US4680866A - Magnetic flux detector correction system - Google Patents

Magnetic flux detector correction system Download PDF

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Publication number
US4680866A
US4680866A US06/811,066 US81106685A US4680866A US 4680866 A US4680866 A US 4680866A US 81106685 A US81106685 A US 81106685A US 4680866 A US4680866 A US 4680866A
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US
United States
Prior art keywords
signal
aircraft
field strength
heading
magnetic heading
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US06/811,066
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English (en)
Inventor
James S. Johnson
Gene A. Albrecht
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Honeywell Inc
SP Commercial Flight Inc
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Honeywell Inc
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Publication date
Application filed by Honeywell Inc filed Critical Honeywell Inc
Priority to US06/811,066 priority Critical patent/US4680866A/en
Assigned to SPERRY CORPORATION reassignment SPERRY CORPORATION ASSIGNMENT OF ASSIGNORS INTEREST. Assignors: ALBRECHT, GENE A., JOHNSON, JAMES S.
Priority to CA000516589A priority patent/CA1239990A/en
Priority to JP61260516A priority patent/JPS62147313A/ja
Priority to EP86309034A priority patent/EP0229468A3/en
Priority to BR8606275A priority patent/BR8606275A/pt
Publication of US4680866A publication Critical patent/US4680866A/en
Application granted granted Critical
Assigned to SP-COMMERCIAL FLIGHT, INC., A DE CORP. reassignment SP-COMMERCIAL FLIGHT, INC., A DE CORP. ASSIGNMENT OF ASSIGNORS INTEREST. Assignors: SPERRY CORPORATION, SPERRY HOLDING COMPANY, INC., SPERRY RAND CORPORATION
Assigned to HONEYWELL INC. reassignment HONEYWELL INC. ASSIGNMENT OF ASSIGNORS INTEREST. Assignors: UNISYS CORPORATION
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01C—MEASURING DISTANCES, LEVELS OR BEARINGS; SURVEYING; NAVIGATION; GYROSCOPIC INSTRUMENTS; PHOTOGRAMMETRY OR VIDEOGRAMMETRY
    • G01C17/00—Compasses; Devices for ascertaining true or magnetic north for navigation or surveying purposes
    • G01C17/38—Testing, calibrating, or compensating of compasses

Definitions

  • the present invention relates to magnetic flux detector system for determining aircraft heading and more specifically for a correction system that compensates for heading errors introduced by aircraft acceleration.
  • Magnetic flux detector systems for determining aircraft heading are well known in the art.
  • flux valves provide accurate heading information only during non-accelerated flight.
  • the pendulous flux valve element is displaced or "hangs-off" the vertical and senses both the earth's horizontal magnetic field and a portion of the earth's vertical magnetic field.
  • Unwanted sensing of the vertical field introduces errors into aircraft heading measurement.
  • Prior art systems simply disengaged the flux valve heading output during periods of accelerated flight that exceeded a predetermined threshold. During periods when the flux valve is disengaged, heading information is obtained from a free gyroscope.
  • prior art systems have the disadvantage of operating for long periods using only free gyro heading information when aircraft acceleration is above a given threshold. Below the acceleration threshold, flux valve heading errors are still introduced as the aircraft experiences small accelerations.
  • the present invention compensates for flux valve heading errors during periods of low level acceleration thereby increasing flux valve heading accuracy and decreases dependence on obtaining heading information from a free gyro.
  • FIG. 1 is a block diagram of the flux valve correction system of the present invention.
  • FIG. 2 illustrates resolving the Earth's magnetic field into horizontal and vertical components.
  • FIGS. 3 and 3A illustrate the flux valve hang off angles.
  • FIG. 4 illustrates heading error in terms of north/east field strength vectors.
  • An aircraft heading correction system which corrects the heading error introduced by flux valve hang off. Magnetic heading and horizontal field strength are derived from flux valve output. Tangent of the dip angle is determined from the horizontal field strength and combined with the aircraft's magnetic north and east accelerations to produce a correction signal which is then subtracted from the flux valve deviation angle signal to provide a corrected magnetic heading.
  • FIG. 1 A block diagram as shown in FIG. 1. It will be understood that the present invention may be implemented as part of a programmable digital computer.
  • flux valve 11 and associated circuitry (not shown) provides signals on lines 12 and 13 to horizontal field strength computation block 14 and to flux valve heading block 15.
  • the flux valve 11 sensitive element is pendulously suspended.
  • the horizontal component has a field strength that varies in magnitude according to geographic location near the earth's surface. Since the horizontal component is always aligned with the magnetic north/south grid line, the flux valve output signals 12 and 13 respectively reduces to:
  • X 1 horizontal field strength ⁇ sine (magnetic heading)
  • Horizontal field strength block 14 Signals representative of values X 1 and X 2 are provided to horizontal field strength block 14 and raw flux valve heading block 15. Signals representative of magnetic North and East acceleration of the aircraft are provided to horizontal field strength block 14 and correction term block 16.
  • the output of the horizontal field strength block 14 (HFS) appearing on line 17 may be expressed as a signal having the form
  • the output of the flux valve heading block 15 may be expressed as a signal having the form Tan -1 [X 1 /X 2 ].
  • the value of horizontal field strength (HFS) may be maintained by updating its value during period of very low aircraft acceleration through the use, for example, of a five minute time constant single pole filter. A shorter time constant filter, for example, 3 minutes may be used during ground alignment.
  • the tangent of the dip angle (i.e., the inclination angle at which the magnetic field enters the earth) may be obtained from a horizontal field strength signal on line 17.
  • the tangent of the dip angle signal (TanDip) appearing on line 19 is calculated by the tangent of the dip angle block 18 utilizing correlation polynomials which relate horizontal field strength to magnetic dip.
  • the magnetic data utilized to develop these polynomials was obtained from Geological Survey Circular 873 and International Geomagnetic Charts and Grid Values (IAGA Bulletin No. 47).
  • Polynomials have been derived for use in calculating the tangent of the dip angle in block 18. Each polynomial corresponds to a different region on the earth's surface.
  • the polynomials take the following form:
  • the correction term block 16 accepts inputs of signals representing tangent of the dip angle on line 19 and the aircraft magnetic North/East acceleration on line 21.
  • the form of the correction term ⁇ ERR on line 20 will be discussed subsequently.
  • the earth's magnetic field (B E ) incident to the north-east down coordinate system has corresponding vector components of horizontal field strength (HFS) and vertical field strength (VFS).
  • HFS horizontal field strength
  • VFS vertical field strength
  • the angle between the B E vector and HFS vector is the dip angle ⁇ .
  • the pendulous element of flux valve 11 When an aircraft accelerates, the pendulous element of flux valve 11 is forced to "hang-off" to an angle approximately equal to the inverse tangent of the aircraft horizontal acceleration divided by the down acceleration.
  • FIGS. 3 and 3A aircraft accelerations are resolved into horizontal components along the approximate magnetic north (FIG. 3) and east (FIG. 3A) coordinates through direction cosines.
  • FIGS. 3 and 3A illustrate the resulting flux valve hang-off angles ⁇ and ⁇ due to north and east acceleration, respectively.
  • the corresponding signals representative of magnetic north and east field strength measurements may be defined as follows:
  • a NM aircraft Magnetic North acceleration
  • a EM aircraft Magnetic East acceleration
  • a DOWN aircraft Down acceleration.
  • correction term block 16 provides the correction term signal ⁇ ERR on line 20.
  • ⁇ ERR is subtracted from deviation angle ⁇ FV in subtraction block 22 during small aircraft accelerations.
  • the output of subtraction block 22 on line 23 is the corrected magnetic heading.

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  • Engineering & Computer Science (AREA)
  • Radar, Positioning & Navigation (AREA)
  • Remote Sensing (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Geophysics And Detection Of Objects (AREA)
  • Measuring Magnetic Variables (AREA)
  • Navigation (AREA)
US06/811,066 1985-12-19 1985-12-19 Magnetic flux detector correction system Expired - Lifetime US4680866A (en)

Priority Applications (5)

Application Number Priority Date Filing Date Title
US06/811,066 US4680866A (en) 1985-12-19 1985-12-19 Magnetic flux detector correction system
CA000516589A CA1239990A (en) 1985-12-19 1986-08-22 Magnetic flux detector correction system
JP61260516A JPS62147313A (ja) 1985-12-19 1986-10-31 航空機の方位修正装置
EP86309034A EP0229468A3 (en) 1985-12-19 1986-11-19 Magnetic flux detector correction system
BR8606275A BR8606275A (pt) 1985-12-19 1986-12-18 Sistema de correcao de rumo de aeronave

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US06/811,066 US4680866A (en) 1985-12-19 1985-12-19 Magnetic flux detector correction system

Publications (1)

Publication Number Publication Date
US4680866A true US4680866A (en) 1987-07-21

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Family Applications (1)

Application Number Title Priority Date Filing Date
US06/811,066 Expired - Lifetime US4680866A (en) 1985-12-19 1985-12-19 Magnetic flux detector correction system

Country Status (5)

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US (1) US4680866A (pt)
EP (1) EP0229468A3 (pt)
JP (1) JPS62147313A (pt)
BR (1) BR8606275A (pt)
CA (1) CA1239990A (pt)

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4750349A (en) * 1985-12-27 1988-06-14 Chrysler Motors Corporation Microcomputer controlled quick ranging technique and digital filter
US5052116A (en) * 1988-02-23 1991-10-01 Alps Electric Co., Ltd. Method and apparatus for measuring azimuth
US5526022A (en) * 1993-01-06 1996-06-11 Virtual I/O, Inc. Sourceless orientation sensor
US5737226A (en) * 1995-06-05 1998-04-07 Prince Corporation Vehicle compass system with automatic calibration
US5878370A (en) * 1995-12-01 1999-03-02 Prince Corporation Vehicle compass system with variable resolution
US5991085A (en) * 1995-04-21 1999-11-23 I-O Display Systems Llc Head-mounted personal visual display apparatus with image generator and holder
US6301794B1 (en) 1999-05-27 2001-10-16 Johnson Controls, Inc. Vehicle compass system with continuous automatic calibration
CN109855623A (zh) * 2019-01-09 2019-06-07 东南大学 基于Legendre多项式和BP神经网络的地磁模型在线逼近方法

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB9002949D0 (en) * 1990-02-09 1990-04-04 Nautech Ltd Autopilot system

Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3425648A (en) * 1966-09-20 1969-02-04 Airborne Navigation Corp Autopilot magnetic heading error correction system
US4006631A (en) * 1974-12-11 1977-02-08 The United States Of America As Represented By The Administrator Of The National Aeronautics And Space Administration Magnetic heading reference
US4024382A (en) * 1975-09-08 1977-05-17 The Laitram Corporation Loran compensated magnetic compass
US4116057A (en) * 1976-12-20 1978-09-26 Gerald Leslie Sullivan Pendulous induction compass transmitter with means to compensate for heading errors in turns due to the vertical component of the Earth's magnetic field and due to two cycle error
US4262427A (en) * 1979-08-10 1981-04-21 Sperry Corporation Flux valve compass system
US4418480A (en) * 1982-04-09 1983-12-06 The United States Of America As Represented By The Administrator Of The National Aeronautics And Space Administration Magnetic heading reference
US4429469A (en) * 1980-11-13 1984-02-07 Alps Electric Co., Ltd. Direction detection apparatus
US4539760A (en) * 1982-10-12 1985-09-10 Plessey Overseas Ltd. Compass

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CA1127304A (en) * 1979-01-24 1982-07-06 Sachinobu Shimizu Apparatus for determining positional coordinates utilizing the terrestrial magnetism as a directional reference
GB2128749B (en) * 1982-10-12 1987-04-15 Plessey Co Plc Electronic compass with tilt compensation

Patent Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3425648A (en) * 1966-09-20 1969-02-04 Airborne Navigation Corp Autopilot magnetic heading error correction system
US4006631A (en) * 1974-12-11 1977-02-08 The United States Of America As Represented By The Administrator Of The National Aeronautics And Space Administration Magnetic heading reference
US4024382A (en) * 1975-09-08 1977-05-17 The Laitram Corporation Loran compensated magnetic compass
US4116057A (en) * 1976-12-20 1978-09-26 Gerald Leslie Sullivan Pendulous induction compass transmitter with means to compensate for heading errors in turns due to the vertical component of the Earth's magnetic field and due to two cycle error
US4262427A (en) * 1979-08-10 1981-04-21 Sperry Corporation Flux valve compass system
US4429469A (en) * 1980-11-13 1984-02-07 Alps Electric Co., Ltd. Direction detection apparatus
US4418480A (en) * 1982-04-09 1983-12-06 The United States Of America As Represented By The Administrator Of The National Aeronautics And Space Administration Magnetic heading reference
US4539760A (en) * 1982-10-12 1985-09-10 Plessey Overseas Ltd. Compass

Cited By (22)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4750349A (en) * 1985-12-27 1988-06-14 Chrysler Motors Corporation Microcomputer controlled quick ranging technique and digital filter
US5052116A (en) * 1988-02-23 1991-10-01 Alps Electric Co., Ltd. Method and apparatus for measuring azimuth
US5526022A (en) * 1993-01-06 1996-06-11 Virtual I/O, Inc. Sourceless orientation sensor
US5991085A (en) * 1995-04-21 1999-11-23 I-O Display Systems Llc Head-mounted personal visual display apparatus with image generator and holder
US5737226A (en) * 1995-06-05 1998-04-07 Prince Corporation Vehicle compass system with automatic calibration
US5878370A (en) * 1995-12-01 1999-03-02 Prince Corporation Vehicle compass system with variable resolution
US20050091861A1 (en) * 1999-05-27 2005-05-05 Johnson Controls Technology Company Vehicle compass system with continuous automatic calibration
US7127823B2 (en) 1999-05-27 2006-10-31 Johnson Controls Technology Company Vehicle compass system with continuous automatic calibration
US20040123475A1 (en) * 1999-05-27 2004-07-01 Johnson Controls Technology Company Vehicle compass system with continuous automatic calibration
US6857194B2 (en) * 1999-05-27 2005-02-22 Johnson Controls Technology Company Vehicle compass system with continuous automatic calibration
US6301794B1 (en) 1999-05-27 2001-10-16 Johnson Controls, Inc. Vehicle compass system with continuous automatic calibration
US6964108B2 (en) 1999-05-27 2005-11-15 Johnson Controls Technology Company Vehicle compass system with continuous automatic calibration
US20060075646A1 (en) * 1999-05-27 2006-04-13 Johnson Controls Technology Company Vehicle compass system with continuous automatic calibration
US6643941B2 (en) 1999-05-27 2003-11-11 Johnson Controls Technology Company Vehicle compass system with continuous automatic calibration
US20060288597A1 (en) * 1999-05-27 2006-12-28 Johnson Controls Technology Company Vehicle compass system with continuous automatic calibration
US7191533B2 (en) 1999-05-27 2007-03-20 Johnson Controls Technology Company Vehicle compass system with continuous automatic calibration
US20070163132A1 (en) * 1999-05-27 2007-07-19 Johnson Controls Technology Company Vehicle compass system with continuous automatic calibration
US7353614B2 (en) * 1999-05-27 2008-04-08 Johnson Controls Technology Company Vehicle compass system with continuous automatic calibration
US20080120054A1 (en) * 1999-05-27 2008-05-22 Johnson Controls Technology Company Vehicle compass system with continuous automatic calibration
US7458166B2 (en) 1999-05-27 2008-12-02 Johnson Controls Technology Company Vehicle compass system with continuous automatic calibration
CN109855623A (zh) * 2019-01-09 2019-06-07 东南大学 基于Legendre多项式和BP神经网络的地磁模型在线逼近方法
CN109855623B (zh) * 2019-01-09 2020-07-31 东南大学 基于Legendre多项式和BP神经网络的地磁模型在线逼近方法

Also Published As

Publication number Publication date
JPS62147313A (ja) 1987-07-01
EP0229468A2 (en) 1987-07-22
EP0229468A3 (en) 1989-04-26
BR8606275A (pt) 1987-10-06
CA1239990A (en) 1988-08-02

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